What Happens When a Neurosurgeon Removes Your Hippocampus

http://www.wired.com/2014/05/heres-what-happens-when-a-neurosurgeon-slurps-out-your-hippocampus/

by ghosh • 12 years ago

111 70 12 years ago

sjclemmy• 12 years ago

Those two kinds of memory mentioned must be concious memory and unconscious memory.

I'd be interested to know about how memory affects ones sense of identity. I'd also like to know if there has been any work that pinpoints the part of the brain that might give insight into self-awareness / consciousness.

amirmc• 12 years ago

The types of memory you're referring to are (more formally) declarative and implicit [1].

Please be wary of 'pinpointing' any regions involved in higher-level functions. It borders on phrenology and despite the vast interest in consciousness, no-one had claimed to have identified regions.

If you haven't come across it before, I'd recommend The Man Who Mistook his Wife for a Hat by Oliver Sacks. Following that, Descartes Error by Antonio Damasio might also be interesting (if you're interested in emotion and reason).

[1] http://en.m.wikipedia.org/wiki/Memory

Sharlin• 12 years ago

"Conscious memory" and "unconscious memory" aren't really well-defined concepts; the actual classification is as follows:

  Explicit (declarative) memory
   - Semantic memory: knowledge of facts and meanings
   - Episodic memory: autobiographic memory of past events
  Implicit memory
   - Procedural memory: motor skills, implicit attitudes

vacri4• 12 years ago

Procedural memory isn't really best termed as 'unconscious' memory. It's memory laid down through practise of a task. There's a lot of different flavours of memory, though most people think of memory as 'recall of factoids'. In terms of 'unconscious' memory, there's a semantic but salient difference between reacting automatically/unconsciously to something (being fearful of dogs because you were bitten once), and voluntarily doing an action but performing it better because of practice (playing a musical instrument).

Regarding anatomy, there's no one part of the brain that is responsible for self-awareness or consciousness (both of which a philosophically difficult to define in the first place), though the frontal lobes (just behind the forehead) are usually implicated in complex thought, concentration, or expressions of personality. There's a lot of overlap in functionality in the brain, when you look at it from a viewpoint of "what bit does this task?" - broken down into its constituent bits, most tasks require a variety of functions to be handled.

"What bit of the brain is involved in waving hello to a friend when we meet them?" would touch on most of the parts, for example - pure perception, pattern recognition, emotion, motor control, decision making, and a few others. The task sounds simple, but it's really quite complex once it's broken down.

ekianjo2• 12 years ago

I'd be interested to know about how memory affects ones sense of identity. I'd also like to know if there has been any work that pinpoints the part of the brain that might give insight into self-awareness / consciousness.

Not exactly answering your question, but one neuroscientist (who got a Nobel Prize... if I remember correctly) who worked on phantom limbs, did a lot of work on damaged brains and one of his patients could not recognize his mother when meeting her face to face, but instantly recognized her when talking with her over the phone. The "wiring" between different parts of the brains was involved to link the memory of the person with the sensory signals, and for that patient the "link" between the visual stimulus and memory was somehow broken while the auditory one was intact. Very interesting.

vacri4• 12 years ago

A colleague of mine had a grandmother who was affected by Alzheimer's. One time she was out and about with her husband and had an episode and couldn't recognise him. She ran off to get police because she felt lost. He found her and was trying to convince her to come with him, but she claimed to the police that he was a stranger and she was frightened.

At this point her husband sang his own name in the manner in which she had during their entire name - this 'got through' and she recognised him again, simply because he sang his name her way, instead of just saying it.

Kronopath• 12 years ago

I'm almost positive you're talking about Vilayanur Ramachandran[0], though he never won a Nobel Prize. He is, however, one of the best lecturers in neuroscience, especially for a layman audience. He's done a few TED talks[1], which I think is what you're recalling.

[0] https://en.wikipedia.org/wiki/Vilayanur_S._Ramachandran

[1] http://www.ted.com/speakers/vilayanur_ramachandran

klapinat0r2• 12 years ago

Oh, this is a conflicted comment I'm posting.

I've recently read a very interesting and, while intuitive, very indepth book on the subject of brains, and brain evolution/commonalities. It covers reactions, active choices, responsibilities, creativity, memory, sleeping patterns, learning and much more.

It's written by a famous Danish brain surgeon, and unfortunately written in Danish.

It's called "Dr. Zukaroffs Testamente" (an intertwined story following the books 500 pages explanations, making it easier to digest), by Peter Lund Madsen.

Why am I commenting even though it's in danish? Because it truly is an amazing book, and one I would've loved to read back when I was deciding which path to choose in life (medschool or other), and in the hope that we may be able to push for an English translation.

If you have any means of reading a Danish book, it's genuinely worth it.

EDIT:

Link: https://translate.google.com/translate?sl=auto&tl=en&js=y&pr...

Filligree• 12 years ago

Well, since I'm Norwegian and can probably read it, I'll thank you for the tip. :-)

jnbiche• 12 years ago

We have a neurologist author who writes kind of similar books: Oliver Sacks. If you've never read any of his books, he's worth checking out.

klapinat0r2• 12 years ago

Thanks, I'll check him out.

paulojreis• 12 years ago

António Damásio (portuguese, but based in USC) is also worth checking out. Descartes' Error is a must read.

septerr• 12 years ago

Another author (and neuroscientist) is David Eagleman. His book - Incognito: The Secret Lives of the Brain, is fantastic.

sateesh• 12 years ago

Another neurologist author whose books are worth checking out is V.S. Ramachandran. His book "Phantoms in the brain" in an interesting read.

vacri4• 12 years ago

As an aside, a way to perform well on the 'tracing-the-star-in-the-mirror' exercise: stop watching what your hand is doing, and instead feel what your hand is doing. Your vision keeps you inside the lines for the most part; where people screw up is making a decision at the vertices. If you look, you'll screw it up, but if you were drawing the star with your eyes closed, you'd know which way the pencil should go.

kevinwang• 12 years ago

Weird, I was just thinking about the difference between "muscle memory" (procedural), and declarative memory. Except I was thinking about people on the opposite end of the spectrum: Hyperthymesia. I was wondering if those with the condition also have superior procedural memory, but if the two forms of memory don't share the same neurological underpinnings, hyperthymesiacs shouldn't have perfect procedural memory, correct?

edit: and as a corollary, I wonder if there is a condition for procedural memory parallel to hyperthymesia for declarative memory. It seems very possible, since hyperthymesia wasn't even recorded until 2006, and a superior procedural memory would be less salient.

robg• 12 years ago

Thanks to Henry we know far more than we ever would have about human memory. He literally gave the memories of his life to science. In return, he got none.

RIP: http://en.wikipedia.org/wiki/Henry_Molaison

brightsize• 12 years ago

Another bio + photos at Find A Grave: http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=450950...

milliams• 12 years ago

I wonder what taking a digital photo "at 20x magnification" actually means. Magnification implies a conversion factor between two comparable objects. There's no sensible comparison between an object 8 inches across and a digital image of that object 5000 pixels across.

Retric2• 12 years ago

It's more obvious at the extremes. At 20,000x magnification your going to show a lot of details normally missed. A high resolution close up shot will often have less detail and than the same number of pixels using some magnification.

Retric2• 12 years ago

I guess I did not get my point across aka not all pixels are equivalent. A camera such as a cellphone camera is designed to take a fairly wide angle picture. It also has a minimum distance it needs to be from an object so moving your finger closer to the sensor stops providing more detail at some point and just provides a blurry mess.

Adding a magnifying lens between the camera and the subject allows you to get more details at the same distance by sacrificing that wide field of view. With the right setup it also allows for higher detailed pictures of the same object aka more details than you would get at the minimum distance for a clear picture. So that 20x zoom refers to the physical optical zoom. You can try this by comparing the highest detailed picture of your hand from your cellphone with and without a magnifing glass.

twic• 12 years ago

The digital photo is captured using a physical sensor. It is meaningful to talk about the ratio of the size of the object, and the size of the image formed on the sensor - this is called the reproduction ratio. It's as relevant now as it was back when images were captured on film and then blown up onto prints. It is the combination of the reproduction ratio and the resolution of the sensor (in pixels per unit distance on the sensor) which determines the resolution of the image (in pixels per unit distance on the object).

That said, it's not clear that this is what is meant here.

mcguire2• 12 years ago

It likely means that they took a photomicrograph through a 20x lens using the highest resolution camera they had handy.

andyjohnson0• 12 years ago

"It was like early retirement, except for the days a Ph.D student named Brenda Milner arrived to test him."

Brenda Milner went on to become a founder of the field of neuropsychology. She's now in her nineties and, according to wikipedia, is still active in research and teaching [1].

[1] http://en.wikipedia.org/wiki/Brenda_Milner#Current_life.2Fre...

icantthinkofone• 12 years ago

They subscribe to reddit.

JoeAltmaier10• 12 years ago

I wonder how this man with no memory could have been considered competent to consent to the preservation of his brain. That part seemed a little like a circus.

Ihmahr• 12 years ago

Just ask him? He wasn't retarded, he just didn't have a working memory. You can also ask him multiple times.

JoeAltmaier10• 12 years ago

You can just ask a child too. What experience did he draw on to make an informed decision? I feel he was definitely taken advantage of.

mcguire2• 12 years ago

And if he gives different answers?

patio112• 12 years ago

He's an adult with many normal reasoning capabilities. Clearly if you were to ask him with regards to other preferences about the disposition of his mortal remains, like "Would you prefer to be buried or cremated? At what cemetery? What type, if any, of funeral service would you prefer?", he'd be capable of giving answers and they'd necessarily be the right ones. If he's capable of answering all of those questions, he's capable of making the decision to donate his brain to science. (After all, there is no conceivable way in which this harms his medical interests. It's not like they're asking him to consent to e.g. limited palliative care options with an eye towards getting his organs in the most usable possible state.)

jessriedel2• 12 years ago

he'd be capable of giving answers and they'd necessarily be the right ones.
(After all, there is no conceivable way in which this harms his medical interests. It's not like they're asking him to consent to e.g. limited palliative care options with an eye towards getting his organs in the most usable possible state.)

Your comment seems to assume that medical or hedonic interests are obviously more important than interests in dignity, aesthetics, or tradition. That's a popular view, but the proper way to handle these sorts of cases does not rest on it.

It's very reasonable to think that one could get a legitimate answer to the question "HM, are you in pain?" without being able to get a legitimate answer to the question "HM, do you want your body used for scientific study?" The "true" HM, which we generally approximate as the man before the accident, might very well consider his dignity (as personally conceived) to be more important than pain.

That's why the correct answer to this, as already pointed out by others, is to rely on his gaurdian as our best guess as to HM's true preferences.

JoeAltmaier10• 12 years ago

Those are all polite, reasonable things with a reasonable range of answers.

But what they did was, saw his brain out on TV, then slice it into grotesque slides that they preserved on permanent display. Lots of people would have a problem with that.

Its questionable if he could be considered an adult. Certainly not an adult like you and me. Not able to 'think about it for a while' for instance. Perhaps the only answers he could give were impulsive ones. It would be childs-play to get him into a frame of mind where he was anxious to be agreeable, then pop the question.

jerf2• 12 years ago

He probably wasn't, so I would assume he had some sort of court-appointed guardian or something (not sure which term is most applicable, but under the circumstances "guardian" may not be that far off...). That would not have been the first decision the guardian would have had to make, after all.

JoeAltmaier10• 12 years ago

At the time apparently the doctors Were his guardians? He was institutionalized without relatives. So conflict of interest is clear.

joveian2• 12 years ago

"Given how deeply all these structures are embedded in the brain, only a neurosurgeon could have destroyed them with such precision." This is just false to the extent it isn't nonsensical. The surgeon claimed that the destruction was precise, but the autopsy actually determined that damage was much more widespread than expected. This has resulted in reconsideration of theories that were based on assumptions that the damage was more limited. In general, when reading anything that mentions H.M. without mentioning this fact it is important to keep that in mind. This article should have taken the new knowledge into account, but continues to present false information.

This is the type of jounalism that helps make it very difficult for popular but incorrect scientific information to be corrected. Another example of this I know of is how REM sleep is commonly referred to as "dream sleep" (including, unfortunately, on Wikipedia last I checked) although the idea that dreaming happens only or even primarily in REM sleep has been considered disproven for multiple decades now and was based on flawed early studies that continue to be described uncritically long after the serious flaws are well known.

On the topic of books: one really excelent (although old now, mostly written in the early 90s and maybe late 80s IIRC) technical book on brain organization is Pierre Gloor's _The Temporal Lobe and Limbic System_. I haven't looked again recently, but I don't know of a comparable work where a neroscientist tries to lay out in depth (it is a neruoscience text) almost everything known about how the brain works together (it is easy to see why; it is a huge amount of work!).

slazaro• 12 years ago

including, unfortunately, on Wikipedia last I checked

I'm gonna be that guy: did you try editing it to make it more accurate?

enraged_camel• 12 years ago

To be fair, last time I tried to make an edit on Wikipedia, it resulted in a huge argument that spanned literally several days, at the end of which I gave up. Note that this was a tiny edit, changing the word order in a sentence or something like that on a rather niche topic.

I haven't bothered trying to edit anything since then.

epochwolf• 12 years ago

It's not worth the effort to edit wikipedia.

aidenn0• 12 years ago

It's extremely hard to get an edit in Wikipedia to stick if you only have primary sources; with a recent, reliable secondary source you often can get it to stick though. If you have a citation in an undergraduate (or even better high school) level neurology textbook then go ahead and make the effort, otherwise don't bother.

nomurrcy• 12 years ago

Are there any other more modern (read: available) books you recommend on the topic? Gloor's work is about $500 presently on amazon and not available electronically.

dewarrn1• 12 years ago

"The surgeon claimed that the destruction was precise, but the autopsy actually determined that damage was much more widespread than expected."

This is flat wrong. Based on structural neuroimaging evidence, Corkin et al. (1997) showed that HM's resection was less extensive than Scoville's notes suggested, not more extensive. The more recent post-mortem analysis of HM's brain (Annese et al., 2014) concurs, and in fact gives an even more conservative estimate of the resection.

As a researcher who studies memory and works with severely amnesic patients, I think that it's important to point out that the precision of HM's lesion was unique in our field because every other bilateral hippocampal amnesic patient has a naturally-occurring lesion. Etiologies vary (herpes simplex encephalitis, anoxia, and, historically, Korsakoff's), but common to each etiology is the potential for widespread damage beyond the hippocampus and medial temporal lobe (MTL). Given that HM's surgery predated sophisticated neuroimaging methods, his case provided researchers of the era the very best possibility of isolating the cognitive processes that depended on the MTL. There have been many methodological and theoretical improvements over the intervening decades, but the work that Brenda Milner, Sue Corkin, and many others carried out with HM was seminal for the field.

Annese, J., Schenker-Ahmed, N. M., Bartsch, H., Maechler, P., Sheh, C., Thomas, N., … Corkin, S. (2014). Postmortem examination of patient H.M.’s brain based on histological sectioning and digital 3D reconstruction. Nature Communications, 5, 3122. doi:10.1038/ncomms4122

Corkin, S., Amaral, D. G., Gonzalez, R. G., Johnson, K. A., & Hyman, B. T. (1997). H.M.’s medial temporal lobe lesion: findings from magnetic resonance imaging. J. Neurosci., 17, 3964–3979.

joveian2• 12 years ago

Thanks for the excellent references; I obviously should have checked my facts before posting. The quote I quoted also makes sense in the context you mention of being in contrast to naturally occurring lesions, which looking again seems clear enough from the story.

I think part of what I was thinking of was from this previous wired article on the study you mention: http://www.wired.com/2014/01/hm-brain-closeup

Particularly Suzane Corkin's quote about shifting the emphasis from the hippocampus to the entorhinal cortex.

The wider damage I was misremembering the extent and cause of looks like it was the combination of the left orbitofrontal legion (possibly but not necessarily connected to the accident or surgery) and the cerebellar atrophy (attributed to anticonvulsant medication). The most recent paper suggest that the cerebellar atrophy was likely to do lifelong medication, but I'm not sure if the higher does of whatever medication he took prior to sugery could have caused that as well. In any case, little if any of the additional damage was likely related to the sugery so as you say that point I made is wrong.

Apologies to all for the misinformation and thanks for the correction and references.

Edit: Also, I suspect I was partly thinking of this article as well and others along these lines (rather than what I actually said): http://hargreaves.swong.webfactional.com/HM.htm

todd8• 12 years ago

I heard about this back in 1971 or 1972 as an undergraduate student. In order to satisfy a general humanities requirement I took a class, 9.01 to be precise (or roughly Intro to Psychology). It turned out to be nothing like I expected. There was only one lecture (two hours) per week on thursday nights. Right away I realized that they were going to be different. The largest lecture hall at MIT (capable of holding half of the entire Freshman class) was packed. People would sit on the stairs and aisles between the fully occupied seats and the head and creator of the Psychology department Professor Hans-Lukas Teuber[1] lectured. It was like listening to the most fascinating episode of Discovery every week. He was an amazing intellect, and he lectured on brain science. During the lecture on memory, he discussed this very case and his experience of meeting this patient. He said that every time he entered the room he had to be re-introduced to the patient. But he said there were hints of the mystery of memory. He showed the patient a half-dollar with an image John F. Kennedy on it and the patient said something that indicated an awareness of JFK (assassinated in 63). He published a few papers with Brenda Milner.

As the semester passed the lecture hall filled more and more until there was finally standing room only, and the final lecture was followed by a standing ovation. It was an absolutely masterful introduction to brain science, delivered in a series of two hour lectures, without ever using notes. Professor Teuber spoke of the need to study the brain scientifically, to treat subjects and patients humanely, and the need for appropriate ethical guidelines in the field. He made me realize that everything we do, from recognizing our grandmother, scratching our back, or recalling an early romance involves fantastic processes in our brain.

After that course, I decided that I would change majors. I went to the Psychology department where (fortunately) they told me that MIT didn't offer an undergrad degree in Psychology. Math and EE/CS was where I stayed.

[1] http://www.nasonline.org/publications/biographical-memoirs/m...

skizm• 12 years ago

For or good measure, Scoville removed H.M.’s amygdalae and other nearby structures as well.

How do they separate the effects of these two? The amygdalae plays a large part in emotion, which probably accounted more for H.M.'s mood changes than the hippocampus. Also memories tied to emotion are more strongly remembered. How do they know they didn't destroy another path to creating memories via the amygdalae? Maybe there are three or more types of memory storage systems. I do agree that the "muscle memory" test was fairly conclusive but the other conclusions drawn are not.

tom_jones• 12 years ago

As phenomenally complex, finely tuned, and resilient as the mind is, there are those with otherwise excellent minds who not only believe such minds were created by random chance, but scoff at the idea that the mind was designed.

What Happens When a Neurosurgeon Removes Your Hippocampus

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